Undead is cool, troll is cool, tauren is huge and fun tanking (had a blast with mine in wrath)... but without question when you say warrior, it's the Orc. The class is pretty much designed around the Orc, it's the bomb.

In WCIII the orc was the strongest first tier unit you could make, and I think WoW held true to that with creating the Orc warriors, it's still the best warrior race in the game.